Nanoparticles don't penetrate skin, study finds

"Breakthrough" claims by cosmetic companies aren't all they're cracked up to be, according to a new study.

Nanotechnology — the science of super-small particles — has featured in cosmetic formulations since the late '80s. Brands claim the technology delivers the "deep-penetrating action" of vitamins and other "active ingredients".

“Using confocal microscopy has allowed us to unambiguously visualise and objectively assess what happens to nanoparticles on an uneven skin surface.

"Whereas earlier work has suggested that nanoparticles appear to penetrate the skin, our results indicate that they may in fact have simply been deposited into a deep crease within the skin sample.

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“The skin's role is to act as a barrier to potentially dangerous chemicals and to reduce water-loss from the body. Our study shows that it is doing a good job of this.

“So, while an unsuspecting consumer may draw the conclusion that nanoparticles in their skin creams are 'carrying' an active ingredient deep into the skin, our research shows this is patently not the case.”

He told the UK's Daily Mail that the research helped to alleviate concerns that potentially toxic ingredients, like those used in sunscreen, can be absorbed into the bloodstream. The particles, he said, are just too big to do that.

But other scientists are not convinced.

Dr Gregory Crocetti, a nanotechnology campaigner with Friends of the Earth Australia, was scathing of the study. “To conclude that nanoparticles do not penetrate human skin based on a short-term study using excised pig skin is highly irresponsible,” he said. “This is yet another example of short-term, in-vitro research that doesn't reflect real-life conditions like skin flexing, and the fact that penetration enhancers are used in most cosmetics. There is an urgent need for more long-term studies that actually reflect realistic conditions.”

Professor Brian Gulson, from Macquarie University in NSW, was was similarly critical. The geochemist's own study, from 2010 and in conjunction with CSIRO, found that small amounts of zinc particles in sunscreen "can pass through the protective layers of skin exposed to the sun in a real-life environment and be detected in blood and urine".

Unsuspecting consumers may draw the conclusion that nanoparticles in their skin creams are 'carrying' an active ingredient deep into the skin ... this is patently not the case

Of the latest study he said: "Even though they used a sophisticated method of laser scanning confocal microscopy, their results only reinforced earlier studies [and had] no relevance to 'real life', especially to cosmetics, because they used polystyrene nanoparticles, and because they used excised (that is, 'dead') pig's skin."

Dr Liz Hanna, of the National Centre of Epidemiology at the Australian National University, offered a different perspective. "There is a school of thought that nanotechnology is not at all harmful ... there are potentially significant benefits from drug-delivery via nanotechnology," she said.

She said, for example, that it has been found you would only need one-fifth the flu vaccination to be effective. "This potential is wonderful as is the potential to avoid skin cancer [by using sunscreen that utilises nanotechnology]."

But Dr Hanna said there are also studies that are highly concerning and directly contradict the findings of Professor Guy. "The greater school of thought is that [such technology] is about weighing up the balance of harm. Is getting skin cancer from sun exposure a lesser evil than the level of damage from nanoparticles?

"We know the long-term damage of sun exposure, but we don't know the long-term damage of nanoparticles ... It's too early to know the magnitude of risks."

Her sentiments echo some of those in the US. Earlier this year, The New York Times said the National Academy of Sciences was calling for further studies on nanomaterials because "not enough is known about their potential health and environmental risks".

Those risks may not be clear for another 20 years, Hanna said. In the meantime, she said we need to take a precautionary approach and be informed about our decisions, because "the jury is still out" on the effects of nanotechnology.

The contradictory claims about sunscreen can make it hard to know what to do this summer. Friends of the Earth Australia advise people to continue to be sun safe — seeking shade, wearing protective clothing, a hat and sunglasses and using broad spectrum SPF 30+ sunscreen.